[sdiy] Voltage Regulators

[harrybissell at wowway.com]

there are two ways to get a self-protected transformer...

impedance limiting... the shorted transformer still has a high enough
impedance to prevent meltdown of the promary circuit (and an even LOWER
impedance)

or "thermal protection" ... a one-time thermal fuse buried inside the
transformer. You REALLY REALLY want good external fuses so that the internal
one does not die !

H^) harry


On Fri, 17 Oct 2008 17:31:13 +0200, Ingo Debus wrote
> Am 17.10.2008 um 10:07 schrieb Florian Anwander:
> 
> > Though it is not very common: I always use fuses between the  
> > transformer and the rectifier.
> 
> If a fuse on the secondary is required or not depends on the  
> transformer type. There are short-circuit-proof types which don't  
> need a fuse (usually very small transformers). For all other  
> transformers a fuse is mandatory. Don't rely on current limiting  
> features of the voltage regulator, the rectifier or filter cap can  
> also cause a short.
> 
> Often there's a symbol printed onto the transformer: two 
> intersecting  circles with two short lines sticking out of one of 
> the circles. If  these two lines are connected on the other side,
>  it's a short-circuit- protected transformer.
> 
> Ingo
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Harry Bissell & Nora Abdullah 4eva